This invention relates generally to spray machines, and particularly to spray machines of the type adapted to reciprocally traverse sheets and webs of material being continuously fed thereby.
Heretofore, machines used in spraying relatively wide, continuous webs or sheets of materials have generally been of either a fixed spray or movable spray type. With a fixed spray machine more than a single spray gun or nozzle must ordinarily be used to achieve lateral uniformity of the applied coating. Thus, the material to be coated is ordinarily fed at a constant velocity beneath a set of laterally spaced spray guns with each gun coating one longitudinal segment of the material. These types of machines have the advantage of minimizing the use of movable parts since there is not need for motors, transmission systems, spray gun tracks or guides.
A principal problem associated with the fixed type of spray machines arises from the tendency of the spray gun nozzles to become partially restricted or even completely clogged with coating fluid. When this occurs the spray gun having a restricted or clogged nozzle commences to apply a thinner or lighter coat to that segment of the material being passed adjacent that particular gun or nozzle. This may result in an easily recognized and noticeable unevenness of coating. In addition, with this type of machine it is difficult simultaneously to prevent both overlapping and lateral spacings between longitudinal coating segments from arising.
To overcome the just mentioned problem characteristic of fixed spray type machines, other machines have been devised having but a single spray gun mounted for reciprocal movement above material to be coated which material is moved therebeneath at a constant rate of speed. Such spray guns either employ a pair of closely spaced nozzles coupled with a manifold, or but a single nozzle. Should one member of the pair of nozzles become restricted the resulting deficiency in applied coating is not readily noticeable since the spray pattern of each nozzle overlaps the other. Even should the movable spray gun employing but a single nozzle become partially restricted the result may not be noticeable since the reduction in coating thickness exists uniformly over the entire width of the coated surface.
Though spray machines employing a traversing spray gun have the very decided advantage just mentioned, they do require moving parts as well as equipment for continuously moving the spray gun. To drive the guns along such a reciprocating path machines have been developed with chains coupled to gear motors and the like for driving a spray gun supporting carriage along a track extending above the material to be coated. These systems have proven relatively bulky and unreliable in operation due to the precision of movement required of the spray gun coupled with the synchronous actuation and deactuation of the gun during acceleration and deacceleration operation which is necessary to prevent excessive coating from occurring while the gun is moving at reduced rates of speed over the side portions of the material. Furthermore, such spray guns have lacked stability since their reciprocal movements have often created moments of inertia causing the gun to wobble as its direction of movement is reversed.
Accordingly, it is a general object of the present invention to provide an improved spray machine.
More specifically, it is an object of the present invention to provide an improved spray machine of the type which includes a spray gun mounted for reciprocal movement along a track beneath or beside which sheets of material are continuously passed for spraying.
Other objects of the invention are to provide a spray machine of the type just described which is relatively stable, inexpensive, reliable in operation and requiring minimal ancillary power supply means.